A MODEL FOR LIBRARY BOOK CIRCULATIONS INCORPORATING LOAN PERIODS

A simple modification of the well-known mixed Poisson model for librar y circulations is proposed which takes account of the periods when a b ook is out on loan, and hence, unavailable for borrowing. It is found that this helps to explain the rapid tailing-off in the upper end of o bserved frequency-of-circulation distributions. Practical consequences of the model include the possibility of investigation of the effects of proposed changes in loan policy and more reliable prediction of fut ure use to assist in, for example, decisions concerning relegation of stock to storage.